DLTS and admittance measurements on CdS/CdTe solar cells

Deep level states can affect the characteristics of thin film solar cells both by their charge and by their recombination. Hence, full solar cell characterisation should include deep states. Deep level transient spectroscopy (DLTS) and admittance spectroscopy (AS) measurements (Y(f, T)) have been made on a series of CdTe/CdS thin film solar cells. Majority and minority trap DLTS was performed between 5 and 330 K revealing semi-shallow to mid-gap traps, depending on the sample. The DLTS results are compared with those of AS in the 100-320 K range at frequencies from 100 Hz to 1 MHz. The energy range probed with the AS is narrower than that of the DLTS method. Both methods give comparable results in the energy range where they overlap. The results are compared with literature data. The difference between cells which received a CdCl2 treatment in air and those which received the treatment in vacuum is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.